Conventional stand-alone locomotives have output power typically ranging from approximately 300 horsepower (for example, locomotives used in mining and tunneling) to 6,000 horsepower (for example, locomotives for long haul cross-country freight trains). In many applications, a number of locomotives may be used in a consist for freight haulage or commuter trains for example.
Conventional railroad locomotives are typically powered by diesel-electric systems or by diesel-hydraulic systems. It is known that a hybrid locomotive or a hybrid locomotive/tender car combination can be used to capture and store energy that is otherwise wasted by incorporating an energy storage system (battery pack, capacitor bank, flywheel assemblies or combinations of these systems). The energy storage system may be charged by an on-board engine, by another hybrid or conventional locomotive in the consist, by a regenerative braking system or by an external source. The stored energy may be used to power the traction motors of the energy storage car or the traction motors of other operative members of the consist.
Donnelly has disclosed the use of a battery-dominant hybrid locomotive in U.S. Pat. No. 6,308,639 which is incorporated herein by reference. Donnelly et al. have disclosed a method of monitoring, synchronizing and optimizing the operation of the locomotive drive train in U.S. patent application Ser. No. 10/649,286 and have also disclosed a method of allocating energy amongst members of a consist in U.S. patent application Ser. No. 11/070,848, both of which are also incorporated herein by reference.
In many areas where rail use is widespread, especially large urban settings, there are special requirements for emissions and noise control which are becoming more and more stringent. Commuter and short haul freight routes typically involve many starts and stops and often involve significant idling time. Many of these routes also may pass over significant grades. While conventional diesel locomotives are achieving higher emissions standards and fuel economy, there are many situations such as partially enclosed or underground stations, tunnels or densely populated areas where low emissions and moderate noise operation or no emissions and low noise operation are required and these requirements cannot always be met by conventional diesel locomotives.
There remains a need for hybrid diesel-electric or diesel-hydraulic locomotives which are capable of operation, including high acceleration capability, at very low or zero emission and low noise levels such as would be required, for example, by commuter trains entering and exiting underground stations.